and immediately tending to this man, jeff bowman, who had both legs blown off. arredondo leaves bowman as he's loaded into an ambulance. >> i was carrying this flag and i just -- my instinct was to go help him and see what i can do. just pray for the angels. >> it's still only minutes after the blasts. photographer john tlumacki finds other people just like carlos arredondo aiding the wounded and snaps a series of unforgettable images, this one of a man applying tourniquets to a woman's leg. and another, this teenager lying on the ground, giving help to total strangers. >> tlumacki doesn't know it but the two victims in the photo he takes are mother and daughter, sell left and sydney corcoran and the man helping sell left is kevin. they're waiting for their sister to cross the finish line. >> i have a vivid memory of seeing my daughter and my friends being blown back, falling backwards. my daughter's arms outstretched like this and falling backwards. and nobody was standing up anymore in front of me. so for a couple of seconds, i just looked left and right and t